| A genetic disorder with characteristics of intellectual disability, childhood hypotonia, severe expressive speech delay and a distinctive facial appearance with a spectrum of additional clinical features. The syndrome is caused by either a point mutation in the euchromatic histone-lysine N-methyltransferase 1 (EHMT1) gene (rarely) or by a microdeletion in the chromosome region 9q34.3 (seen in more than 85% of cases), leading to the loss of the entire gene. This gene encodes an enzyme that modifies histone function and is essential for normal development. Larger deletions (greater than 1mb) are associated with more severe symptoms. |
